The vast majority of video tape recorders (VTRs) in use today are analog machines which record video (and accompanying audio) on tape, so that the playback of that video must be sequential. While digital VTRs may come into wide use shortly, it is more likely that random access media such as computer hard drives will replace current VTRs because of the advantages provided by random access.
U.S. Pat. No. 5,241,428 of the present inventor discloses a BVR (Buffered Video Recorder) which digitally records (buffers) video on a random access medium so that a previously stored portion of a program can be played from the buffer while the currently broadcasting portion of the program is simultaneously recorded. In one of the modes of operation of the BVR the viewer can speed the playback of portions of the material to be played-back from the buffer in order to "catch up" with the live broadcast. In another mode the viewer can playback portions of the buffered material in slow motion to do an instant replay. While conventional VTRs permit the video portion of recorded video with audio to be "speed-searched", i.e. viewed at many times real time (typically 9 or more times real time), they do not play the audio portion while the video is being speed-searched, because the audio would change pitch and would therefore be impossible to understand. Similarly, when video with audio is played at a slower speed than it was recorded at, the pitch will change. It becomes impossible to understand speech when the playback rate is even one half the normal rate.
A new speech compression technology is now available from Voxware Inc. of Princeton, N.J., that permits digitized speech to be played at any speed from 1/5 to 5 times real time without a change of pitch. But at about 3 times real time the audio is likely to be too fast to understand if every word is played.